Below, there are 5 activities. Complete each activity, and answer the questions. Write your answers onto a sheet of paper. Write your name on the paper. Hand it up at the end of the session. After you have completed the activities, resume work on your personal home page (lab 6).
Some of the activities can be run from the Windows command line. You usually bring this up as follows: Start > All programs > Accessories > Command prompt. These activities are labelled "(Windows)" below.
But most of the activities are run from our Linux file server, cosmos.ucc.ie
.
These activities are labelled "(cosmos)" below.
You don't need to reboot your PC to enjoy these activities! Simply use the Secure
Shell Client (ssh), which we used when changing our Unix passwords during
Induction Week. From Windows choose All programs > SSH Secure Shell >
Secure Shell Client. Choose Quick Connect. In the dialog that pops up,
the host name needs to be cosmos.ucc.ie and the port number must be 22.
Then click Connect. You'll be prompted for your password. Afterwards, if another
dialog pops up, click OK.
Before you proceed, let me remind you of UCC's Acceptable Usage Policy. Do not misuse your new-found knowledge. If you do, we will have no option but to come down hard on you!
(Windows) You can find out a lot of information about how your desktop PC is
connected to the Internet by running a utility called ipconfig
.
Type the following at the command prompt:
ipconfig /allLook at the output, and answer these questions:
netstat
is another utility that gives
some interesting information. In fact, it gives overwhelming amounts of information.
Run it as follows to get a summary:
netstat -s
(Windows) By all means run it at the Windows command prompt.
(cosmos) But run it on cosmos too, read through the output, and use it to answer the following questions:
(cosmos) Network administrators often need to check whether two hosts can communicate.
A basic way to do this is to use the ping
utility.
ping
uses a protocol called ICMP to repeatedly
send echo request packets to the target
host; the target host sends echo reply packets back. ping
estimates the round-trip time (rtt) and any packet loss.
ping
either TCD's web server (134.226.1.30) or UCD's (193.1.172.59) or
NUIG's (140.203.7.89) or UL's (193.1.101.61). Pick one
at random, and only ping
it once: we do not want to be accused of attacking
their systems!
Type ping
followed by the IP address.
If cosmos can communicate with this host, lots of output will appear.
Interrupt ping
(using Ctrl+C) after about 10 lines.
Some summary statistics will be displayed.
ping
?Here's a couple of optional, 'fun' activities:
ping
.
(Windows or cosmos) You can run nslookup
to ask DNS to find the IP
address that corresponds to a given domain name, e.g.
nslookup www.tcd.ie
Read the output carefully when answering these questions.
www.ryanair.com
and the IP address for
www.ryanair.ie
. What has this company done and why?
(Use your browser to visit these two hosts, if it helps.)nslookup
on www.google.ie
. What has this
company done and why?
(Windows or cosmos)
If you give nslookup
an IP address instead of a domain name, it may also
perform the reverse mapping, e.g.
nslookup 193.1.172.59
(Digression. On machines running Unix/Linux, such as cosmos, the commands
host
and dig
are also available to do much the same
thing that nslookup
does. Try them if you like.)